1. Field of the Invention
The invention relates to a data programming circuit, and more particularly to a data programming circuit of a memory.
2. Description of the Related Art
A Phase Change Memory (PCM) is a non-volatile memory with high speed, high capacity and low energy consumption, wherein a plurality of PCM cells of the PCM cell is formed by phase change material, such as chalcogenide etc. The phase change material can be switched between two states, a crystalline state and an amorphous state, with the application of heat, wherein the phase change material has different resistances corresponding to the crystalline and amorphous states respectively, wherein the resistances respectively represent different stored data.
In general, the PCM cell has a relatively high resistance in an amorphous state, which may be used to represent that a data stored in the PCM cell is a binary bit “0”. On the contrary, the PCM cell has a relatively low resistance in a crystalline state, which may be used to represent that a data stored in the PCM cell is a binary bit “1”.
However, for a PCM with a plurality of multi-level memory cells, each memory cell stores at least two-bits data (such as “00”, “01”, “10” and “11”). The multi-level PCM cell needs four different crystalline states in order to represent or identify the two-bits data stored in the PCM cell. Hence, for a PCM cell, the complexity of a programming method is increased when a category of the crystalline state is increased.